Indeed, to understand something is to see it in its relations to other things! How does it operates? How does it function? What consequences follow from it? What causes it?
We need to go beyond the information given to make inferences, connections, and associations!
A middle school student who can explain why steam, water, and ice, though superficially different, are the same chemical substance has a better understanding of H2O than someone who cannot!
Students should be able to transfer their abstract knowledge into giving good accounts that provide a useful framework, logic, and telling evidence to support claims!
Understanding is thus not mere knowledge of facts but inference about why and how, with specific evidence and logic, insightful connections.